What that means to a normal person is that Mojave is a codominant trait and so is already a het. If you don't understand the terminology, then why are you paying extra for it? A Mojave is already heterozygous for the Mojave trait. A snake that is homozygous for the Mojave trait is a mostly white snake with blue eyes.
The fact of the matter is, whether she's doing it on purpose or not, she IS ripping you off because you are not getting what you paid for. If you paid extra money for a car that was supposed to be red with white racing stripes would you be satisfied receiving one that was flat gray?